So it turned out to be a be a pretty quick resoration in the end as it is what it is, a Khyber pass special and an out and out wall hanger, It's fully functional but it'd be beyond unwise to fire it. All the bits were indeed there except one barrel pin which I had to make, the rest of the lock cleaned up well, the barrel bore was a little rusy and blocked, not with powder and ball thankfully and couple of days full of vinegar sorted that out. The mainspring swivel needed a bit of welding and reshaping to get that functioning and for the stock I decided the best thing was to epoxy it together, pin it to the barrel let it set then make good the joint. The wood was very old and dry as a bone so got plenty of pure linseed oildiluted with a little pure turps and came up....ok.
Was thinking to give it to a pal of mine as a present but got quite attached to it as it came together, surely everyone needs one example of a khyber pass firearm in their collection.
It kind of mostly resembles an East India Company F pattern musket but with a Brown Bess flavour so will have a place next to my genuine F pattern.
Thanks again to Mark for letting me have it, it's found a good home and not going anywhere.